PROJECT SUMMARY Potassium channels are key determinants of neuronal excitability. A multitude of potassium channels with distinctly different properties have been identified by molecular cloning, but large gaps remain in our understanding of how this molecular diversity corresponds to the rich physiological diversity of potassium channels in neurons. Identification of molecular substrates underlying native neuronal K+ channels remains a major challenge in neurobiology with important implications for understanding regulation of neuronal excitability and development of novel therapeutic targets. Among the myriad potassium channels, the TASK channels of the K2P subfamily are particularly notable for their wide distribution throughout the central nervous system where they contribute neuronal background (or `leak') potassium currents. These TASK-like background currents set neuronal resting potential and input resistance, and affect firing patterns, action potential characteristics and responses to synaptic inputs. TASK channels allow dynamic modulation of cell excitability by physicochemical factors (e.g., H+, glucose), endogenous neuromodulators (e.g., neurotransmitters, endocannabinoids) and clinically relevant drugs (e.g., anesthetics). They have been implicated in various physiological processes (e.g., control of breathing, arousal) and advanced as potential targets for distinct anesthetic actions (e.g., hypnosis, immobilization). To date, the study of native TASK channels has been hampered by a dearth of selective pharmacological tools; tentative identification has been based on complicated biophysical and pharmacological criteria involving combinations of non-selective channel modulators. TASK knockout mice have confirmed important physiological roles for these channels, but do not allow for dynamic bidirectional modulation of TASK currents during experiments, a key step in assessing the potential of these channels to serve as therapeutic targets. In this proposal, we seek to develop high throughput screening assays for identification of specific openers and blockers for mammalian TASK channels - specifically for TASK-1 and TASK-3 homomeric channels and TASK-1/TASK-3 heteromeric channels. Good evidence exists for the presence of all three combinations in therapeutically important native neuronal systems. We expect specific blockers will find immediate application in experimental identification and characterization of TASK currents in the nervous system, while openers are likely to have significant therapeutic potential. PROJECT NARRATIVE Diseases including epilepsy, anxiety and psychotic disorders involve pathological hyperexcitability of the nervous system. Modulators of ion channels, which generate and regulate neuronal signaling, have proven highly useful for treating these diseases. The research proposed in this application aims to develop a novel class of therapeutically relevant ion channel modulators that may have application in the treatment of nervous system diseases or as novel anesthetics. [unreadable] [unreadable] [unreadable]